About OpenPuzzle.org
A free library of mathematical puzzles for children in kindergarten through grade 6. Every one opens in a browser with nothing to install and nothing to sign up for, and keeps working when the connection does not.
OpenPuzzle.org makes mathematical puzzle apps that simultaneously engage the brilliant child and the struggling adult. Their quality comes not from flashiness or addictive reward loops but from the intellectual joy of solving something challenging. The puzzles are free and without ads. We don't do glitz.
Parents should expect ethical behaviour from educators. The priority should not be to capture the most children and keep them hooked for as long as possible. The priority should be to give children inspired experiences and then let them go.
OpenPuzzle.org offers ethically grounded puzzle experiences. They encourage curiosity, celebrate tough problem-solving, and respect your child's time.
Mission
To create a free library of deep mathematical puzzles.
Privacy
None of your data is collected, used, or sold. Your progress is stored locally in your browser. The downside is that it can be lost and is not transferable between devices yet (we are thinking about how to make that happen).
Philosophy
Many of the puzzles found in apps, books, and websites have been invented, copied, and adapted so many times that it is often hard to trace who originally created them. Where there is a clear connection to the origin of a puzzle, we try to keep credits.
Our goal is to harness the power of AI to offer these widely-known puzzles for free — and free people from platforms that charge unreasonable prices, run predatory advertisements, or collect personal data.
The code is predominantly generated by artificial intelligence, yet everything is checked and curated by humans.
About Us
Sasha Kaurov (PhD) is a father searching for quality educational experiences for his son. Professionally, he's an astrophysicist and science communicator. He creates free education resources that are open to everyone.
Gordon Hamilton (MMath, PhD) designs board games like Santorini and curricular math puzzles like you'll find here. The puzzles are classroom-tested and teacher-approved. Watch the documentary "Put your students in a pickle!" to see him in action.
Every puzzle
Below is every puzzle on the site, youngest grade first. Each one opens a page with more for grown-ups: the rules, what it gives a class to practise, and ideas for using it in a lesson.
Stained GlassSkip-counting turned into a picture: the pattern each times table draws across a hundred square.
Finding ZeroEvery number turned over says how far zero is, so the hunt closes in by reasoning rather than guessing.
Longest RoadThe longest road is found by walking away from anywhere twice — a guess by eye, then a count to check it.
No Three in a LineFit in as many towers as the dots can hold with never three on one straight line — and start to see the slanted lines nobody draws.
Disco BallsA shelf of empty seats, one per way of ordering a number’s prime factors: fill them all and you have counted the orderings by hand.
Mondrian PuzzleEvery rectangle painted is a multiplication, and the score is the gap between the biggest one and the smallest.
Slug SaladEach slug eats a number equal to everything it has eaten before it — addition with a reason to check and go back.
Stirring PaintDeduction with no arithmetic in the way — colours, directions and jumps, worked out until every loop closes.
Hitome's GardenEvery line has just two ways to go, and the walls they make decide which flowers end up sharing a bed.
Picasso BrushA stroke is only as long as one end number divided by the other, so covering the paper is a hunt for factors.
Voronoi IslandsEvery spot on the island belongs to the nearest iguana, so the game is where to stand to hold more than half of it.
Fractured FractionsOne point cuts the whole picture at once, and every piece has to come out holding the fraction written on it.
GalaxeaTwo of the three dice are the sides of a rectangle — and the game is which two, and where to hang it.
Diversity CityEvery zone counts the different sizes next door, and the city scores their average — so the fewer, busier zones win.
Lozenge LandRead a flat tiling as deep stone, and cut the cheapest stairs that let the water climb it.
Balanced ZebraBoth colours have to multiply out to the same number, and then to the largest that shape allows.
KajitsuCutting fruit into pieces of a given size and symmetry: every morsel has to fold or spin onto itself.
ZebraHerds multiply together, so three threes beat one nine — and a stone left on its own throws itself away.
MinotaurEvery step of the string has to be longer than the one before, and it may never touch itself: how many steps can the way to the Minotaur take?
Ariadne's StringTwo threads cross one hall, each step longer than that thread’s last, and the first with no longer step left loses.
GozenYour next number is forced, so a prime is always coming — and on a prime only a square nobody watches will do.
Nothing matches all three. Widen one of the filters.
Using it with a class
- A link or a class page
- Each puzzle’s page has a link that opens the whole puzzle, and the code to put it on a class page as a frame. Whoever opens it stays inside that puzzle.
- On paper
- Print any board from the browser for a paper copy of the puzzle, laid out for a pencil.
- Shared devices
- Progress is kept in the browser on the device, not in an account, so people who share a tablet share one record of what is solved. The gear on the home screen erases it, all at once or one puzzle at a time.
- No connection
- Installed from the browser as an app, it keeps every puzzle on the device and works without a connection.
License
Both the puzzles and their code implementations are protected under Creative Commons license, CC BY-NC-ND.
Get in touch
Tell us what worked, what confused someone, or what you would like to see. We read every message. hello@openpuzzle.org